Camshaft phasers are used in internal combustion engines in order to vary the timing of the combustion chamber valves. Adapting the timing to the current load lowers fuel consumption and reduces emissions. A commonly employed model is the vane-type adjuster. Vane-type adjusters have a stator, a rotor and a driving gear. The rotor is usually non-rotatably joined to the camshaft. The stator and the driving gear are likewise joined to each other, whereby the rotor is situated coaxially to the stator as well as inside the stator. The rotor and the stator have radial vanes that form oil chambers which counteract each other, which can be filled with oil under pressure and which allow a relative movement between the stator and the rotor. Moreover, the vane-type adjusters have various sealing lids. The assembly comprising the stator, driving gear and sealing lid is secured by means of several screwed connections.
U.S. Pat. Appln. No. 2009/0173297 A1 discloses a hydraulic camshaft phasing device that has a driving gear and, coaxially thereto, a stator with two rotors arranged concentrically to the stator. Here, the stator can be configured so as to consist of a single part or else of several components. The rotors and the stator have radially oriented vanes. In this manner, the stator, together with the rotors, forms working chambers that can be filled with a hydraulic medium under pressure, so that a relative rotation occurs between the appertaining rotor and the stator around the rotational axis of the camshaft phaser. A partition wall that is arranged between the rotors as a component of the stator axially separates the rotors from each other. Each rotor can be connected to a camshaft. In this case, the camshaft is configured as a hollow shaft, whereas the other camshaft is made of solid material. Both camshafts are arranged concentrically with respect to each other. The cams that are associated with the camshafts are connected to their camshaft in such a way that a relative circumferential rotation of the cams or of the associated camshafts can occur relative to each other, so that the timing of the inlet and outlet valves associated with the cams can be adjusted continuously and variably.
The vanes of the rotors and the vanes of the stator have a certain surface which is exposed to pressure when the working chambers are filled with a hydraulic medium, and thus it is exposed to a force in the circumferential direction that gives rise to the relative rotation. The response behavior of such a hydraulic camshaft phaser is determined by this surface and by the pressure of the hydraulic medium that is generated by a pressure-medium pump.